New operating techniques in modern day neurosurgery require both a main operator and an assistant to view the same operating area at the same time. The main operator and assistant should be able to view the same field of vision. This requirement is difficult to meet in practice as the microscope has to be able to be oriented in all directions in space and must be capable of being operated in all these orientations.
The Japanese manufacturer Olympus has developed a microscope which can be used in neurosurgery in which the solution is essentially based on the use of a magnification system which does not give rise to any stereoscopic splitting. This makes the development of such a microscope easier on the one hand but gives rise to serious defects which are not acceptable to the users in certain fields of application. One such defect is for example the fact that the three dimensional impression varies with the magnification.
Application publication U.S. 2001/0010592 A1 discloses a stereomicroscope in which the optical channels of observation for the main operator and assistant are split in front of the respective objective and magnification systems. The optical viewing paths for the main operator, after passing through a first main objective, are deflected into the horizontal, while a corresponding magnification system for the main operator is arranged horizontally. The assistant microscope is arranged underneath the main microscope. A disadvantage of this is that the free working interval underneath the microscope (i.e. the distance between the microscope and the object which is to be observed) is reduced and the overall height of the microscope as a whole is increased. As a separate main objective is also required for the assistant microscope, this microscope also proves to be relatively complicated in the provision of the respective optical components.